Abstract: Objective To investigate the changes of content and mRNA expression of gelsolin and proliferation activity of T-lymphocyte in spleen of mice with severe burn injury, so as to determine the optimum intervention time of gelsolin. Methods Eighty male BALB/c mice were divided into sham injury group and burn group according to the random number table, with 40 mice in each group. Mice in burn group were inflicted with 15% total body surface area full-thickness scald (hereinafter referred to as burn) on the back. Immediately after injury, mice in burn group were hypodermic injected with 1 mL normal saline, with iodophor smeared on back once a day to prevent infection. Mice in sham injury group were sham injured without fluid infusion and smearing iodophor. At post injury hour (PIH) 0 (immediately), 8, 24, 48, and 72, spleen of 8 mice of each group were harvested aseptically, respectively. Proliferation activity of T-lymphocyte was determined with methyl-thiazolyl-tetrazolium colorimetry method; gelsolin content of spleen was determined with enzyme-linked immunosorbent assay; mRNA expression of gelsolin of spleen was determined with real-time fluorescent quantitative reverse transcription polymerase chain reaction. Data were processed with analysis of variance of factorial design, one-way analysis of variance, LSD test and Bonferroni correction. Results (1) There was no significant difference in proliferation activity of T-lymphocyte in spleen of mice in two groups at PIH 0 (P>0.05). Proliferation activity of T-lymphocyte in spleen of mice in sham injury group was significantly higher than that in burn group at PIH 8, 24, 48, and 72 (with P values below 0.05). There was no significant difference in proliferation activity of T-lymphocyte in spleen of mice in sham injury group at each time point post injury (F=0.756, P>0.05). Proliferation activity of T-lymphocyte in spleen of mice in burn group at PIH 8 was 0.12±0.04, significantly lower than that at PIH 0, 24, 48, and 72 in the same group (0.73±0.07, 0.56±0.07, 0.51±0.09, and 0.59±0.07, respectively, with P values below 0.05). (2) There was no significant difference in gelsolin content of spleen of mice in two groups at PIH 0 (P>0.05). Gelsolin content of spleen of mice in sham injury group was significantly higher than that in burn group at PIH 8, 24, 48, and 72 (with P values below 0.05). There was no significant difference in gelsolin content of spleen of mice in sham injury group at each time point post injury (F=1.083, P>0.05). Gelsolin content of spleen of mice in burn group at PIH 8 was (11.9±2.6) pg/mg, significantly lower than that at PIH 0, 24, 48, and 72 in the same group [(37.7±2.9), (19.9±4.0), (24.1±4.1), and (24.6±4.0) pg/mg, respectively, with P values below 0.05]. (3) There was no significant difference in mRNA expression of gelsolin of spleen of mice in two groups at PIH 0 (P>0.05). The mRNA expressions of gelsolin of spleen of mice in sham injury group were significantly higher than those in burn group at PIH 8, 24, 48, and 72 (with P values below 0.05). There was no significant difference in mRNA expression of gelsolin of spleen of mice in sham injury group at each time point post injury (F=0.413, P>0.05). The mRNA expression of gelsolin of spleen of mice in burn group at PIH 8 was 0.307±0.064, significantly lower than that at PIH 0, 24, 48, and 72 in the same group (0.944±0.023, 0.625±0.091, 0.744±0.104, and 0.821±0.072, respectively, with P values below 0.05). Conclusions Severe burn injury could induce decrease of proliferation activity of T-lymphocyte and content and mRNA expressions of gelsolin in spleen of mice, and all of them decreased into the lowest at PIH 8. Optimum intervention time of gelsolin for severe burn would be before PIH 8.